This invention relates to an ink jet recording apparatus being placed on a reciprocatively movable carriage for jetting ink drops toward recording paper in response to print data, thereby printing on the recording paper and a cleaning control method in the recording apparatus and in particular to a cleaning control technique for eliminating an atmosphere valve communicating with a capping unit for sealing a recording head and simplifying an ink discharge sequence from the recording head executed by the capping unit. It also relates to a recording apparatus for solving a problem of contaminating recording paper, etc., by waste ink stored in the capping unit that can be produced by eliminating the atmosphere valve.
An ink jet recording apparatus produces relatively small noise at the printing time and moreover can form small dots at a high density and therefore recently has been used for various types of printing including color printing.
Such an ink jet recording apparatus comprises an ink jet recording head which receives supply of ink from an ink cartridge and is reciprocated in a main scanning direction and a paper feeder for carrying recording paper in a subscanning direction orthogonal to the recording head and jets ink drops from the recording head based on print data, thereby recording on the recording paper.
A recording head capable of jetting black, yellow, cyan, and magenta inks, for example, is placed on a carriage and the color ink jetting percentage can be changed for executing full color printing as well as text printing in black ink.
The described ink jet recording head involves a problem of clogging nozzle orifices and causing a print failure because of a rise in ink viscosity caused by evaporation of a solvent from the nozzle orifices, solidification of ink deposition of dust, mixing of air bubbles as ink pressurized in a pressure generating chamber is jetted to recording paper as ink drops from the nozzle orifices for printing. Thus, this kind of ink jet recording apparatus comprises a capping unit for sealing the nozzle formation face of the recording head at the non-printing time.
The capping unit functions as a lid for preventing ink in the nozzle orifices of the recording head from being dried. In addition, if the nozzle orifices are clogged, the capping unit also provides an ink jet capability recovery function of sealing the nozzle formation face by the capping unit and sucking and discharging ink from the nozzle orifice by a negative pressure from a suction pump for unclogging the nozzle orifices.
The forcible ink suction and discharge treatment executed for unclogging the recording head is called cleaning operation; to restart printing after a halt for a long time or when the user recognizes a print failure and, for example, operates a cleaning switch, the cleaning operation is executed. A negative pressure produced by the suction pump is added and ink is sucked from the recording head and discharged into the capping unit, then the nozzle formation face is wiped out by a wiping member formed of a rubber material, etc., for example.
The capping unit is placed, for example, at an end of the recording apparatus out of a print area (home position) and is mounted on an elevating mechanism that can be lifted up to the nozzle formation face side of the recording head by a driving force of the carriage accompanying a move of the carriage to the home position side.
A recovery function of applying a drive signal not related to printing to the recording head for idly jetting ink drops, called flushing operation, is also provided. It is executed every given period for recovering an irregular meniscus if the irregular meniscus occurs in the proximity of the nozzle orifice of the recording head and preventing clogging as viscosity of ink is increased in the nozzle orifice less jetting ink drops during printing.
FIG. 12 is a top view of the configuration of a capping unit 71 in related art used for the described cleaning operation. The capping unit 71 is placed at an end (home position) out of the placement position of a paper guide plate 72 forming a print area.
A recording head mounted on a carriage (not shown in FIG. 12 and described later) is guided by a guide rod so that it can move just above the paper guide plate 72 and the capping unit 71.
The capping unit 71 comprises a cap member 73 formed of a flexible rubber material, etc., that can seal the nozzle formation face of the recording head positioned just above the capping unit 71 and has a function of sealing the nozzle formation face of the recording head at the non-printing time for preventing ink in the nozzle orifices firm being dried and a function of receiving a negative pressure from a suction pump (described later) and forcibly discharging ink from the recording head at the cleaning operation time.
Thus, a cap holder 74 on which the cap member 73 is mounted is placed on an elevating mechanism that can be lifted up to the nozzle formation face side of the recording head by a driving force of the carriage accompanying a move of the carriage to the home position side.
An ink absorbing sheet 75 is housed in the cap member 73 and the cap member 73 is formed at an inner bottom part with an ink suction port 76. One end of a tube forming a part of a tube pump (not shown) is connected to the ink suction port 76.
The cap member 73 is formed at an inner bottom part with an atmosphere port 77. A tube 78 is connected at one end to the atmosphere port 77 and connected at an opposite end to a valve 79. The valve 79 is opened and closed by a valve body 80 and the valve body 80 is placed in a state normally closing the valve 79 by a spring 81. The valve body 80 is molded integrally with a valve rod 82 and the valve rod 82 is held so that it can be slid axially for opening and closing the valve.
An end of the valve rod 82 abuts a stopper 84 formed on a frame 83, whereby the valve 79 is opened against the repulsion force of the spring 81.
A cleaner holder 87 comprising a wiping member 86 made of a rubber material, for example, that can wipe out the nozzle formation face of the recording head mounted on the carriage accompanying a move of the carriage is placed on the print area side adjacent to the capping unit so that it can be advanced to or retreated from the move path of the recording head.
FIG. 13 shows the cleaning sequence of the recording head in the related art, executed by the described capping unit 71. The cleaning operation in the recording apparatus in the related art will be discussed according to a flowchart shown in FIG. 13.
First, when cleaning treatment is started, operation unnecessary for the cleaning treatment, such as paper feed operation, is all inhibited at step S11. In this state, the cleaner holder 87 is moved in the horizontal direction and the wiping member 86 is advanced onto the move path of the recording head.
As the carriage is moved, the wiping operation of wiping out the nozzle formation face of the recording head by the wiping member 86 is executed at step S12, whereby dust, paper powder, and the like adhering to the nozzle formation face are removed.
Subsequently, the carriage is moved to the capping position and large suction operation of ink from the recording head is executed at step S13. FIGS. 14A to 14D schematically show the large suction operation executed at step S13 and later. In FIG. 14, numeral 91 denotes the recording head, numeral 73 denotes the cap member, and numeral 79 denotes the valve connected to the atmosphere port 77 made in the inner bottom part of the cap member by the tube 78.
Further, numeral 92 denotes the suction pump; waste ink can be discharged into a waste tank 93 through the tube pump 92 connected to the ink suction port 76 made in the inner bottom part of the cap member.
First, FIG. 14A shows a state in which the recording head 91 is sealed by the cap member 73. Subsequently, as shown in FIG. 14B, the atmosphere valve 79 connected to the cap member 73 is closed and in this state, the suction pump 92 is driven for a predetermined time for accumulating a negative pressure in the cap member 73. In this state, ink is sucked and discharged into the cap member 73 by the accumulated negative pressure at step S14 in FIG. 13.
Thus, ink is discharged from the recording head 91 as shown in FIG. 14C and an amount of ink matching the negative pressure is discharged into the inner space of the cap member 73 as shown in FIG. 14D.
Thus, when the pressure in the cap member 73 rises to such an extent that it is brought close to the atmospheric pressure, control goes to step S15 shown in FIG. 13 and the atmosphere valve 79 is opened and the suction pump 92 is driven.
FIGS. 15A and 15B show this state. That is, if the atmosphere valve 79 is opened as shown in FIG. 15A, some air flows into the cap member 73 through the valve 79 by the action of the negative pressure remaining in the cap member 73, as shown in FIG. 15B, and the inside of the cap member 73 becomes the atmospheric pressure.
As the suction pump 92 is driven, the ink discharged into the cap member 73 is discharged into the waste tank 93. In this case, while the suction pump 92 is rotated at low speed and bubbles produced by inflow of air from the valve 79 are suppressed, ink in the cap member 73 is discharged.
After the steps are executed, the wiping operation at step S16 in FIG. 13 is executed. In this case, the cleaner holder 87 is moved in the horizontal direction and the wiping member 86 is advanced to the move path of the recording head.
As the carriage is moved, the nozzle formation face of the recording head 91 is wiped out by the wiping member 86 and ink adhering to the nozzle formation face of the recording head 91 is scraped away by the wiping member 86.
At step 817 following the wiping operation, the suction pump 92 is driven with the cap member 73 released from the recording head 91. FIG. 15C shows this state; the ink remaining in the cap member 73 is discharged into the waste tank 93.
At steps S13 and S14 described above, when the large suction operation is executed and ink is sucked and discharged from the recording head, a large amount of ink remains in the cap member 73 and thus if the atmosphere valve 79 is opened, the ink in the cap member 73 is sucked to the suction pump 92 and is discharged into the waste tank 93 while producing bubbles, as shown in FIG. 15B. Therefore, the bubbles enter the nozzle orifices of the recording head 91 and destroy meniscuses formed in the nozzle orifices; this is a problem.
Then, in the cleaning sequence in the related art, to restore the destroyed meniscuses to their former shapes, a sequence at step S18 and later steps in FIG. 13 is executed subsequently.
That is, at step S18, the first small suction operation is executed for the recording head 91. Also in this case, the recording head is sealed by the cap member and the suction pump is driven for a shorter time than that at the large suction time for giving a weak negative pressure to the inside of the cap member for discharging ink although not shown.
Subsequently, step S19 is executed like step S14; at step S19, the bubble degree can be lessened because the amount of ink remaining in the cap member is small.
At steps S21 and S22, the wiping operation is executed and the suction pump is driven in almost similar manners to those at steps S16 and S17. Steps S18 to S22 are repeated as many times as required, whereby the meniscuses of the nozzle orifices destroyed by the bubbles are restored.
It is determined at step S23 that steps S18 to S22 have been repeated a predetermined number of times, control goes to step S24 at which the finish wiping operation is executed, whereby the meniscuses are recovered to an almost complete state. At step S25, the recording head is moved to a position not opposed to the cap member and the suction pump 92 is driven for discharging the ink in the cap member.
Next, fine vibration is given to the recording head, for example, by forward and reversely turning a carnage motor at step S26, promoting dissolving of the bubbles taken into the nozzle orifices by the cleaning operation, etc., in ink.
After the fine vibration is given, a flushing hold flag is turned on at step S27 and a flushing hold timer (not shown) is started at step 828.
Thus, the flushing operation is inhibited for a predetermined time of time-out of the flushing hold timer or more and the bubbles produced by the cleaning operation are dissolved in the ink for preventing a print failure from occurring.
The recording head is moved to the capping position and the nozzle formation face of the recording head is sealed by the cap member at step S29 and any inhibited operation other than the cleaning treatment is enabled at step S30.
When the flushing hold timer counts the predetermined time, for example, after the expiration of the time required for the bubbles in the vicinity of the nozzle orifices to be dissolved in ink and disappear, flushing is executed for cleaning at step S32 and the flushing hold flag is turned on at step S33, then a standby mode is entered.
The ink jet recording apparatus having the cleaning function as described above comprises the atmosphere valve 79 communicating with the cap member forming the capping unit and adopts a sequence of executing the ink suction operation by a negative pressure and then opening the valve for discharging ink.
Thus, it is necessary to place the atmosphere valve 79 adjacent to the cap member 73 as shown in FIG. 12. As previously described with reference to FIG. 12, the valve body 80 molded integrally with the slidable valve rod 82 is urged in a dosed state by the spring 81 and the end part of the valve rod 82 abuts the stopper 84 formed on the frame 83, whereby the atmosphere valve 79 is opened against the repulsion force of the spring 81.
Therefore, a large number of steps are required for managing and assembling the assembly parts making up the atmosphere valve and moreover the percent defective is relatively high; this is a problem. Further, in the connection tube from the cap member the atmosphere valve, the water content evaporation degree is large and it is difficult to sufficiently retain the moisture in the cap member at the non-printing time; this is also a problem.
Further, as described above, to discharge ink from the cap member after the large suction operation is executed and ink is sucked and discharged from the recording head, a large amount of ink remains in the cap member, thus a phenomenon in which the ink in the cap member 73 is sucked to the suction pump 92 and is discharged to the waste tank 93 while producing bubbles occurs as shown in FIG. 15B.
Thus, the problem of the bubbles entering the nozzle orifices of the recording head and destroying the meniscuses formed in the nozzle orifices is involved. Therefore, in the cleaning sequence in the related art, to restore the destroyed meniscuses to their former shapes, it is necessary to repeat the loop of steps S18 to S22 shown in FIG. 13 more than once and further execute the appurtenant sequence consisting of steps S24 to S28.
Therefore, the time required for the cleaning operation also becomes large, resulting in bothering the user, for example, irritating the user
On the other hand, control as described above is executed, whereby the evil effect produced as bubbles occur can be avoided, but when the atmosphere valve is eliminated according to the above context, a situation occurs wherein the capping unit is brought away from the nozzle formation face with waste ink stored in the cap member to perform the cleaning operation. In such a situation, the effect of vibration, etc., is received and ink is leaked from the inside of the capping unit to the outside and particularly adheres to the outer peripheral surface of the cap member forming the sealing part of the capping unit and remains thereon; this is a problem.
The remaining ink is deposited on the recording head, developing a problem of the ink dripping down on recording paper placed on the print area during printing and contaminating the recording paper at times.
On the other hand, if the nozzle formation face is wiped out by the wiping member after ink is sucked and discharged from the recording head, there is also a problem of scattering the ink scraped away from the nozzle formation face to the capping unit side by the reaction of mechanical return of the wiping member, thus a problem of waste ink deposited and remaining on the outer peripheral surface of the cap member is also involved.
With the recording apparatus comprising a capping unit into which a cap member forming a seating part of the capping unit and a cap holder for holding the cap member are assembled, ink enters the gap formed between the cap member and the cap holder and the discharging effect of ink in the gravity direction can be provided to some extent, thus the problem of ink dripping down on recording paper from the recording head during printing, etc., and contaminating the recording paper as described above is relatively hard to occur.
However, with the recording apparatus comprising integral-type a capping unit with no gap between a cap member and a cap holder, escape of ink in the gravity direction is prevented, so that the problem of ink remaining on the outer peripheral surface of the cap member occurs and the problem of contaminating recording paper by the action described above occurs remarkably.
It is therefore a first object of the invention to provide an ink jet recording apparatus for simplifying an ink discharging sequence from a recording head, executed by a capping unit with the above-described atmosphere valve eliminated, and a cleaning control method in the recording apparatus.
And it is a second object of the invention to provide an ink jet recording apparatus adapted to aggressively escape ink to remain on the outer peripheral surface of a cap member in the gravity direction for decreasing the amount of ink deposited on a recording head to prevent recording paper, etc., from being contaminated even if the atmosphere valve is eliminated.
In order to achieve the first object, according to the invention, there is provided an ink jet recording apparatus comprising:
a recording head having a face on which nozzle orifices from which ink drops are ejected in accordance with print data are formed;
a carriage for mounting the recording head;
a capping unit having a sealing face for sealing the nozzle formation face of the recording head, and having an inner space connected to a suction pump;
a wiping member for wiping the nozzle formation face; and
a controller for controlling the capping unit so as to (i) seal the nozzle formation face with the sealing face, (ii) drive the suction pump to apply negative pressure into the inner space to discharge ink from the nozzle orifices, and (iii) keep the sealing state until a first predetermined time period required for restoring the negative pressure to the atmospheric pressure elapses after the ink has been discharged.
In this case, when the capping unit seals the nozzle formation face of the recording head and sucks and discharges ink from the nozzle orifices by the action of the negative pressure from a suction pump, it is desired that the wiping member is advanced onto the move path of the recording head.
Preferably, the wiping member moves from an initial position to a second position where is on a moving path of the recording head when the capping unit executes the ink discharge operation.
Preferably, the controller separates the capping unit from the nozzle formation face such that the sealing face is inclined with respect to the nozzle formation face after the first predetermined time period has elapsed.
Preferably, the ink jet recording apparatus further comprises a waste ink tank connected to the capping unit via the suction pump. The controller drives the suction pump to discharge ink stored in the inner space into the waste ink tank when the capping unit is separated from the nozzle formation face.
Preferably, the controller controls the wiping member so as to wipe the nozzle formation face after the capping unit has been separated from the nozzle formation face.
Preferably, the ink jet recording apparatus further comprises a carriage motor for driving the carriage reciprocatively between a print region and a home position. The capping unit is moved toward the recording head to seal the nozzle formation face by using driving force of the carriage motor for moving the carriage toward the home position. The capping unit is separated from the nozzle formation face by using driving force of the carriage motor for moving the carriage toward the print region. The carriage motor has a first speed established when the capping unit is separated from the recording head and a second speed, which is faster than the first speed, established when the carriage passes through the second position of the wiping member.
Preferably, the controller drives the suction pump again after the nozzle formation face has been wiped out by the wiping member in order to discharge ink stored in the inner space of the capping unit.
In order to achieve the first object, according to the invention there is also provided a cleaning control method for an ink jet recording apparatus which comprises: a recording head having a face on which nozzle orifices from which ink drops are ejected in accordance with print data are formed; a carriage for mounting the recording head; a capping unit having a sealing face for sealing the nozzle formation face of the recording head, and having an inner space connected to a suction pump; and a wiping member for wiping the nozzle formation face, the method comprising the steps of:
sealing the nozzle formation face with the capping unit;
driving the suction pump to apply negative pressure into the inner space to discharge ink from the nozzle orifices; and
waiting until a first predetermined time period required for restoring the negative pressure to the atmospheric pressure elapses while keeping a state that the nozzle formation face is sealed with the capping unit.
Preferably, the cleaning control method further comprises the steps of:
separating the capping unit from the nozzle formation face after the first predetermined time period has elapsed; and
driving the suction pump to discharge ink stored in the inner space of the capping unit into an ink waste tank synchronously with the separating step.
Preferably, the cleaning control method further comprises the step of wiping the nozzle formation face with the wiping member executed after the separating step has been executed.
Alternatively, the cleaning control method further comprises the steps of:
separating the capping unit from the nozzle formation face after the first predetermined time period has elapsed; and
wiping the nozzle formation face with the wiping member.
Preferably, the cleaning control method as set forth in claim 19, further comprising the step of driving the suction pump again to discharge ink stored in the inner space of the capping unit after the wiping step has been executed.
According to the above ink jet recording apparatus and the above cleaning control method in the recording apparatus, the atmosphere valve is eliminated and after the step of sucking and discharging ink from the recording head, the step of holding the seating state of the nozzle formation face of the recording head by the capping unit and waiting until the expiration of a predetermined time required for the inner space of the capping unit to be restored to the atmospheric pressure is eliminated. Thus, a necessary and sufficient amount of ink increased in viscosity can be discharged.
The recording head sealed by the capping unit is unsealed and the suction pump is driven, whereby the ink in the capping unit is discharged into the waste tank.
Therefore, the factor of producing bubbles in ink in the capping unit as shown in the cleaning sequence in the related art is eliminated, so that the evil effect produced by bubbles of ink as the atmosphere valve is opened as in the recording apparatus comprising the atmosphere valve in the related art can be removed.
Therefore, the small suction operation of ink, etc., for restoring meniscuses to their former shapes need not be executed and it is made possible to simplify the cleaning sequence.
In order to achieve the second object, preferably, the capping unit includes a cap member made of a flexible material, which is to be abutted against and seal the nozzle formation face, and a cap holder made of a hard material and having a circumferential wall for holding the cap member therein. The cap member has a portion protruded from an upper end face of the circumferential wall. A dimension between a top end of the protruded portion and the upper end face of the circumferential wall is larger than a dimension between a lower end of the protruded portion and an outer edge of the circumferential wall.
Preferably, the protruded portion of the cap member has a cross section shaped into a substantially triangle.
In this case, ink to remain on the outer peripheral surface of the cap member can be effectively escaped in the gravity direction. Thus, the amount of ink to remain on the outer peripheral surface of the cap member can always be decreased and it is made possible to minimize the problem of allowing the ink remaining on the outer peripheral surface of the cap member to adhere to the recording head and contaminate recording paper.
Preferably, the capping unit includes a spring for urging the cap member toward the nozzle formation face. The cap holder includes a spring holder formed on a outer face of the circumferential wall of the cap holder for holding one end of the spring. The spring holder has at least one opening for leading ink remaining on an outer circumferential face of the cap member toward a gravity direction.
Preferably, an upper face of the spring holder and the upper end face of the circumferential define a substantially identical plane.
In this case, the amount of ink to remain on the upper face of the spring holder can be decreased effectively.
Preferably, a plurality of openings are adjacently arranged along the outer face of the circumferential wall of the cap holder.
In this case, ink to remain on the upper face of the flat spring holder can be discharged through any of the openings in the gravity direction, contributing to the ink amount reducing effect on the upper face of the spring holder where ink easily remains.
Preferably, the opening is shaped into a polygon forming comers therein.
In this case, the guiding and excluding action of ink can be promoted by capillary action at the comers of the inner faces of the opening.
Preferably, the cap member and the cap holder are integrally formed by either an insert molding or a two-color molding.
Preferably, the flexible material is either an elastomer or rubber.